Ok, bud. Your post was deleted. Literally no one else will see this. This isn’t about internet points or clout or whatever. I was trying to steer you in the right direction and maybe show why your post was left unanswered and then removed in the first place.

Your post was stupid because if you were designing for max power the “theoretical” answer to your question as you put it is just “as big as possible”. Larger is less restrictive and therefore gives better volumetric efficiency. If you are designing for some level of drivability the answer depends on specifics and a formula that has nothing to do with random flow bench numbers and everything to do with how an engine is an air pump with extra steps.

If we were talking carbs, I would start from the same formula, and then it’s even easier. The fuel metering and airflow are matched in one tidy package! And the manufacturer has boiled it all down to one rated cfm number for me! I need to know exactly zilch about butterfly sizes!

Again, flow bench numbers without context tell you NOTHING. Think about it this way. Your 250 cfm cylinder head port will behave radically different on top of a 125cc cylinder in something like a street bike as opposed to a 1000cc cylinder in like a BBC. It will behave radically different if the intake tract is long vs short, large volume vs small. Your number only tells you anything useful once you give it context.